A pin type bridge anchors the string thru the bridge and the ball end of the string makes contact with the inside of the top itself, while a pinless bridge just pulls from the bridge I'm not an engineer, but that results in a shearing action..If the strings are fastened pinless or not, they will "load" the top, but in my opinion, the pinless bridge is much more apt to shear the bridge off of the top. I'm at work, but I'm a member--- so please no comments about my being a guest